Keeping the interior of a vehicle at a comfortable temperature is an important aspect of providing driver comfort and safety. In some cases, it is also desirable to maintain the interior at a comfortable temperature while the vehicle is parked. Most notably, long-haul truckers often sleep in the cab of the truck during the required 10-hour rest period.
One way of keeping the cab of the truck cool when the truck is parked is to maintain the engine at an idle and run the truck's main air conditioning system. However, this long-term idling results in increased fuel consumption, pollution, engine maintenance, and reduced battery life. Further exasperating the problem is that the truck's engine must be run at a higher RPM than idle to produce enough current to support auxiliary sleeper air conditioning. Thus, if the RPM of the engine is not increased above idle, the batteries will operate in deficit.
As a result of the environmental considerations discussed above, federal regulations will soon require maintaining interior cab temperatures of a Class 8 vehicle in an engine off (or “no-idle”) condition. To maintain driver comfort, many Class 8 vehicles have been equipped with two air conditioning systems: a first system for use when the engine of the truck is running, and a second system for use when the truck is parked and the engine is off. Thus, there exists a need for optimizing vehicle air conditioning systems, particularly for optimizing the fuel efficiency of Class 8 vehicles having two air conditioning systems.